Coyote Point Systems Equalizer GX Series, Administration Manual

Page: 29 / 866

Load Balancing
Load balancing is based on the policy selected. The policies can be split up into two categories:
1. round robin
2. everything else
Round robin simply selects the next server in the list with no regard for how busy that server may
be.
Other load balancing policies use proprietary algorithms to compute the load of a server and then
select the server with the least load server.
Although the load balancing policies are proprietary, they use the following factors in their
calculation:
l
Active connections
- The number of connections a server currently has active and the number
of connections that it tends to have open.
l
Connection latency
- The amount of time that it takes a server to respond to a client request.
l
Health check performance values
- Depending on the health checks configured, this may be not
used at all, or it can completely define how the load is calculated.
Once a load is calculated, Equalizer distributes incoming requests using the relative loads as
weights.
sv00
Load = 50
sv01
Load = 50
sv02
Load = 50
Equalizer calculated loads, so the request distribution will be approximately equal
sv00
Load = 100
sv01
Load = 50
sv02
Load = 25
sv01 and sv02 above are uneven loads. sv01 is twice as loaded as sv02, so it will receive about
half the requests.
The load calculations happen approximately every 10 seconds and server weights are adjusted
accordingly. During that 10 second interval, the relative server loads remain the same, but probe
and health check information is collected about the servers so that it can be used for the next
calculation.
The load calculation works the same for Layer 4 and Layer 7 clusters (at the server-pool level –
and these can be shared between all cluster types).
Copyright © 2014 Coyote Point Systems, A Subsidiary of Fortinet, Inc.
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Equalizer Administration Guide